Arpack-ng is a collection of Fortran77 subroutines designed to solve large scale eigenvalue problems.

Important Features:

Single and Double Precision Complex Arithmetic Versions for Standard or Generalized Problems.

Routines for Banded Matrices - Standard or Generalized Problems.

Routines for The Singular Value Decomposition.

Example driver routines that may be used as templates to implement numerous Shift-Invert strategies for all problem types, data types and precision.

It is free software. arpack-ng (like arpack) is released under the BSD 3 clauses license.

This project is a joint project between Debian, Octave and Scilab in order to provide a common and maintained version of arpack.

Indeed, no single release has been published by Rice university for the last few years and since many software (Octave, Scilab, R, Matlab...) forked it and implemented their own modifications, Arpack-ng aims to tackle this by providing a common repository and maintained versions.